MESSENGER fly-by of Mercury

Earlier today the Messenger spacecraft flew past the planet Mercury (images to follow as they are released).
The photo here is ~15h before closest approach
Credit NASA / APL

This is a long term and complicated mission...
Launched in 2004 Messenger aims to go into orbit around Mercury in 2011 and collect data for a whole year.

Remember, Mercury is the closest planet to the Sun. If you were to aim a craft directly, the Sun's enormous gravitation would cause so much acceleration that the craft could not carry enough fuel to slow down in time to enter mercurial orbit.

So what do you do? You launch it sideways into orbit around the Sun, use gravity assists (flybys) and short engine burns (using the precious fuel) to gradually nudge the craft into a diminishing solar orbit until it is captured by the gravitation field of Mercury.

From the mission website:

To become the first spacecraft to orbit Mercury, MESSENGER must follow a path through the inner solar system, including one flyby of Earth, two flybys of Venus, and three flybys of Mercury. This impressive journey will return the first new spacecraft data from Mercury since the Mariner 10 mission over 30 years ago.

See the Messenger site for this timeline of the mission:


One more Mercury fly-past (29th Sept. 2009) and two more fuel burns (DSMs - Deep Space Maneuvers) before it goes into orbit (18th Feb 2011).